Semiconductor device

ABSTRACT

A first power supply terminal P is provided with an internal wiring connection portion 31A, an upright portion 31B which is joined to the internal wiring connection portion 31A, an inclined portion 31C which is joined to the upright portion 31B and an external wiring connection portion 31D which is joined to the inclined portion 31C. A second power supply terminal N is provided with an internal wiring connection portion 32A, an upright portion 32B which is joined to the internal wiring connection portion 32A, an inclined portion 32C which is joined to the upright portion 32B and an external wiring connection portion 32D which is joined to the inclined portion 32C. The upright portion 31B of the first power supply terminal P and the upright portion 32B of the second power supply terminal N are arranged so as to face each other, with a predetermined interval kept therebetween.

TECHNICAL FIELD

The present invention relates to a semiconductor device such as a powermodule.

BACKGROUND ART

A power module is a device in which a pair of switching elements areconnected in series to a power supply to obtain an output from betweenthe pair of switching elements. Such a power module is, for example,used for an inverter circuit which forms a driving circuit to drive anelectric motor. The electric motor is used as, for example, a powersource of an electric vehicle (including a hybrid car), a train, anindustrial robot and the like. The power module is also applied to aninverter circuit that converts electric power generated by a solarbattery, a wind power generator and other power generators(particularly, a private electric generator) so as to match the electricpower of a commercial power supply.

For the switching elements of power modules, devices using Si (silicon)semiconductors have been conventionally used. However, there has been aproblem of losses in the devices at the time of power conversion, andthe situation is that a further improvement in efficiency of the devicesusing Si materials is no longer feasible.

Therefore, a power module using, as its switching elements, powerdevices using SiC (silicon carbide) semiconductors has been proposed.The SiC power devices are capable of conducting a high-speed ON/OFFoperation because switching speed is high. Consequently, a currentquickly decreases at the time of switch-off so that switching loss canbe reduced.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent Application

Publication No. 2003-133515

Patent Document 2: Japanese Patent Application Publication No.2004-95769

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, high-speed switching by the SiC power devices causes a newproblem that an increase in surge voltage at the time of switchingoccurs.

The surge voltage V is, as shown in the following formula (A), given bya product of a self-inductance L which internal wiring of the powermodule has and a differential (di/dt) of a current i by a time t(current change ratio per hour).V=L·(di/dt)  (A)

The higher the switching speed, the greater the change ratio (di/dt) ofthe current i, so that the surge voltage V is increased. When the surgevoltage loads the devices with a voltage not less than a breakdownvoltage, the devices may be broken. Moreover, when the surge voltage isgreat, there are also concerns of an increase in EMI (electromagneticinterference) noise and a reduction in reliability.

Therefore, in order to reduce surge voltage while applying high-speedswitching elements such as SiC devices, it is necessary to reduce theself-inductance L which the internal wiring of the power module has.This problem is common not only to power modules but also tosemiconductor devices having switching elements. Of course, also insemiconductor devices having switching elements using Si semiconductors,a reduction in surge voltage is a significant problem.

An object of the present invention is to provide a semiconductor devicecapable of realizing a power module with a small self-inductance ofinternal wiring.

Means for Solving the Problems

A first semiconductor device according to the present invention includesa first power supply terminal and a second power supply terminal whichare arranged so as to be adjacent in a predetermined one direction in aplan view, an output terminal which is arranged, with an interval kept,in an orthogonal direction to the one direction with respect to thefirst power supply terminal and the second power supply terminal in aplan view, a first circuit which includes a first switching elementelectrically connected between the first power supply terminal and theoutput terminal, and a second circuit which includes a second switchingelement electrically connected between the output terminal and thesecond power supply terminal.

The first power supply terminal includes a first internal wiringconnection portion and a first external wiring connection portion whichare flat plate-shaped and arranged so as to face each other, with aninterval kept, in a vertical direction along a plan view direction, anda first coupling portion which couples an edge portion of the firstinternal wiring connection portion and that of the first external wiringconnection portion on the side of the second power supply terminal. Thesecond power supply terminal includes a second internal wiringconnection portion and a second external wiring connection portion whichare flat plate-shaped and arranged so as to face each other, with aninterval kept, in a vertical direction along a plan view direction, anda second coupling portion which couples an edge portion of the secondinternal wiring connection portion and that of the second externalwiring connection portion on the side of the first power supplyterminal. The first coupling portion and the second coupling portioneach include plate-shaped facing portions facing each other, with apredetermined interval kept therebetween.

During a transition period when the first switching element inside thefirst circuit is switched from a conductive state to a cutoff state andthe second switching element inside the second circuit is switched froma cutoff state to a conductive state, a current flows from the externalwiring connection portion to the internal wiring connection portion inone of the first power supply terminal and the second power supplyterminal, and a current flows from the internal wiring connectionportion to the external wiring connection portion in the other of them.

Also during a transition period when the second switching element insidethe second circuit is switched from a conductive state to a cutoff stateand the switching element inside the first circuit is switched from acutoff state to a conductive state, a current flows from the externalwiring connection portion to the internal wiring connection portion inone of the first power supply terminal and the second power supplyterminal, and a current flows from the internal wiring connectionportion to the external wiring connection portion in the other of them.

During the above-described transition period, a direction at which acurrent flows at the plate-shaped facing portion of the first couplingportion in the first power supply terminal and a direction at which acurrent flows at the plate-shaped facing portion of the second couplingportion in the second power supply terminal are reverse to each other.The plate-shaped facing portion of the first coupling portion and theplate-shaped facing portion of the second coupling portion at which acurrent flows in a mutually reverse direction face each other, with apredetermined interval kept therebetween. Accordingly, during thetransition period, self-inductance of the first power supply terminaland self-inductance of the second power supply terminal can cancel eachother out, by which it is possible to provide a semiconductor devicewith a low self-inductance of internal wiring.

In one preferred embodiment of the present invention, the first externalwiring connection portion is arranged above the first internal wiringconnection portion. The first coupling portion includes a flatplate-shaped first upright portion which rises up from the edge portionof the first internal wiring connection portion on the side of thesecond power supply terminal and a flat plate-shaped first inclinedportion which extends diagonally upward from an upper edge portion ofthe first upright portion so as to be further spaced away from thesecond power supply terminal as it moves upward and which is coupled tothe edge portion of the first external wiring connection portion on theside of the second power supply terminal. The second external wiringconnection portion is arranged above the second internal wiringconnection portion. The second coupling portion includes a flatplate-shaped second upright portion which rises up from an edge portionof the second internal wiring connection portion on the side of thefirst power supply terminal and a flat plate-shaped second inclinedportion which extends diagonally upward from an upper edge portion ofthe second upright portion so as to be further spaced away from thefirst power supply terminal as it moves upward and which is coupled toan edge portion of the second external wiring connection portion on theside of the first power supply terminal. The first upright portion andthe second upright portion constitute the plate-shaped facing portionswhich face each other.

In one preferred embodiment of the present invention, the plate-shapedfacing portions which face each other are each formed in a rectangularshape when viewed in the one direction, a clearance between theplate-shaped facing portions which face each other is 2 mm or less, theplate-shaped facing portion is 5 mm or more in height and theplate-shaped facing portion is 14 mm or more in width. In thisconstitution, self-inductance of the first power supply terminal andself-inductance of the second power supply terminal can be efficientlycancelled out.

In one preferred embodiment of the present invention, the first circuitincludes a first element bonding conductor layer to which the firstpower supply terminal is electrically connected and also the firstswitching element is bonded via a first solder layer. The second circuitincludes a second element bonding conductor layer to which the outputterminal is electrically connected and also the second switching elementis bonded via a second solder layer and a second power supply terminalconductor layer to which the second power supply terminal iselectrically connected. The semiconductor device includes a firstconnection metal member in which a surface which is an opposite side toa surface of the first switching element which is bonded to the firstelement bonding conductor layer is electrically connected to the secondelement bonding conductor layer and also a second connection metalmember in which a surface which is an opposite side to a surface of thesecond switching element which is bonded to the second element bondingconductor layer is electrically connected to the second power supplyterminal conductor layer.

In this constitution, a first electrode (for example, a drain electrode)of the first switching element is electrically connected to the firstpower supply terminal via the first element bonding conductor layer. Afirst electrode (for example, a drain electrode) of the second switchingelement is electrically connected to the output terminal via the secondelement bonding conductor layer. A second electrode (for example, asource electrode) of the first switching element is electricallyconnected to the output terminal via the first connection metal memberand the second element bonding conductor layer, and also electricallyconnected to a first electrode (for example, a drain electrode) of thesecond switching element. A second electrode (for example, a sourceelectrode) of the second switching element is electrically connected tothe second power supply terminal via the second connection metal memberand the second power supply terminal conductor layer.

In one preferred embodiment of the present invention, the first circuitalso includes a first diode element bonded to the first element bondingconductor layer via a third solder layer. The second circuit alsoincludes a second diode element bonded to the second element bondingconductor layer via a fourth solder layer. The first connection metalmember is constituted so that a surface which is an opposite side to asurface of the first switching element and that of the first diodeelement which are bonded to the first element bonding-conductor layer iselectrically connected to the second element bonding conductor layer.The second connection metal member is constituted so that a surfacewhich is an opposite side to a surface of the second switching elementand that of the second diode element which are bonded to the secondelement bonding conductor layer is electrically connected to the secondpower supply terminal conductor layer.

In this constitution, the first electrode (for example, a drainelectrode) of the first switching element and the first electrode (forexample, a cathode electrode) of the first diode element areelectrically connected to the first power supply terminal via the firstelement bonding conductor layer. The first electrode (for example, adrain electrode) of the second switching element and the first electrode(for example, a cathode electrode) of the second diode element areelectrically connected to the output terminal via the second elementbonding conductor layer. The second electrode (for example, a sourceelectrode) of the first switching element and the second electrode (forexample, an anode electrode) of the first diode element are electricallyconnected to the output terminal via the first connection metal memberand the second element bonding conductor layer and also electricallyconnected to the first electrode (for example, a drain electrode) of thesecond switching element. The second electrode (for example, a sourceelectrode) of the second switching element and the second electrode (forexample, an anode electrode) of the second diode element areelectrically connected to the second power supply terminal via thesecond connection metal member and the second power supply terminalconductor layer.

In one preferred embodiment of the present invention, the firstconnection metal member and the second connection metal member are eachconstituted with a conductive plate-shaped body. In this constitution,as compared with a case where a wire is used as the first connectionmetal member, it is possible to reduce self-inductance of internalwiring and also reduce thermal resistance of a semiconductor device.

In one preferred embodiment of the present invention, the firstconnection metal member and the second connection metal member are eachmade of a copper plate or a copper plate to which nickel-plating isapplied.

In one preferred embodiment of the present invention, the firstconnection metal member and the second connection metal member are eachfrom 0.8 mm or more to 2.0 mm or less in thickness. In thisconstitution, it is possible to reduce efficiently thermal resistance ofthe semiconductor device.

In one preferred embodiment of the present invention, there are alsoincluded a heat radiating plate and a substrate bonded to the heatradiating plate. The first element bonding conductor layer, the secondelement bonding conductor layer and the second power supply terminalconductor layer are formed on a surface of the substrate which isopposite to the side of the heat radiating plate.

In one preferred embodiment of the present invention, the first solderlayer and the second solder layer are each from 0.08 mm or more to 0.10mm or less in thickness. In this constitution, as compared with a casewhere the first solder layer and the second solder layer are eachthicker than 0.10 mm in thickness, heat generated at the first switchingelement or the second switching element can be easily transmitted to theheat radiating plate. Accordingly, it is possible to reduce thermalresistance of the semiconductor device.

In one preferred embodiment of the present invention, the first solderlayer and the second solder layer are made of Sn—Ag—Cu-based solder.

In one preferred embodiment of the present invention, the first circuitand the second circuit are assembled to the substrate. And, a surface(hereinafter, it may be referred to as a rear surface) which is anopposite side to a surface of the heat radiating plate on which thesubstrate is bonded is polished and flattened.

A heat sink and other cooling means are often mounted on the rearsurface of the heat radiating plate. In this constitution, as comparedwith a case where the heat radiating plate is not flattened (thinned) bypolishing the rear surface, heat generated at the first switchingelement or the second switching element is easily transmitted to thecooling means mounted on the rear surface of the heat radiating plate.Accordingly, it is possible to reduce thermal resistance of thesemiconductor device.

In one preferred embodiment of the present invention, the first internalwiring connection portion of the first power supply terminal is providedwith a first base portion and a first comb-shaped terminal whichprotrudes from the first base portion to the side of the outputterminal. The second internal wiring connection portion of the secondpower supply terminal is provided with a second base portion and asecond comb-shaped terminal which protrudes from the second base portionto the side of the output terminal. The first comb-shaped terminal isbonded to the first element bonding conductor layer (for example, byultrasonic bonding), by which the first power supply terminal iselectrically connected to the first element bonding conductor layer. Thesecond comb-shaped terminal is bonded to the second power supplyterminal conductor layer (for example, by ultrasonic bonding), by whichthe second power supply terminal is electrically connected to the secondpower supply terminal conductor layer.

In this constitution, the first power supply terminal and the secondpower supply terminal can be easily connected respectively to the firstelement bonding conductor layer and to the second power supply terminalconductor layer, as compared with a case where a wire is used.

A second semiconductor device according to the present inventionincludes a plate-shaped insulation substrate which is formed in asubstantially rectangular shape, a circuit which is loaded on theinsulation substrate and includes a semiconductor element, a first powersupply terminal and a second power supply terminal which are mounted soas to be adjacent on the insulation substrate in a predetermined onedirection of the insulation substrate in a plan view and which supplypower to the circuit, and an output terminal which is mounted on theinsulation substrate, with an interval kept, in an orthogonal directionto the one direction with respect to the first power supply terminal andthe second power supply terminal in a plan view and which takes outputfrom the circuit.

The first power supply terminal includes a first internal wiringconnection portion and a first external wiring connection portion whichare each formed in a flat plate-shape and arranged so as to face eachother, with an interval kept, in the thickness direction of theinsulation substrate, and a flat plate-shaped first coupling portionwhich couples an edge portion of the first internal wiring connectionportion and that of the first external wiring connection portion on theside of the second power supply terminal. The second power supplyterminal includes a second internal wiring connection portion and asecond external wiring connection portion which are each formed in aflat plate-shape and arranged so as to face each other, with an intervalkept, in the thickness direction of the insulation substrate, and a flatplate-shaped second coupling portion which couples an edge portion ofthe second internal wiring connection portion and that of the secondexternal wiring connection portion on the side of the first power supplyterminal. The first coupling portion and the second coupling portioneach include a plate-shaped facing portion having a flat plate portionfacing each other, with a predetermined interval kept therebetween. Alsoin this constitution, as with the foregoing first semiconductor device,it is possible to provide a semiconductor device with a lowself-inductance of internal wiring.

In one preferred embodiment of the present invention, a clearancebetween the plate-shaped facing portions is smaller than a distancebetween the first external wiring connection portion and the secondexternal wiring connection portion.

The above-described object of the present invention, or other objects,features and effects will be clarified by a description of preferredembodiments given by referring to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative plan view which shows an internal structure ofa power module according to one preferred embodiment of the presentinvention.

FIG. 2 is a right side view of FIG. 1.

FIG. 3 is a rear view of FIG. 1.

FIG. 4 is an illustrative sectional view taken along line IV-IV in FIG.1.

FIG. 5 is an illustrative sectional view taken along line V-V in FIG. 1.

FIG. 6 is an illustrative enlarged sectional view taken along line VI-VIin FIG. 1.

FIG. 7 is an illustrative perspective view for describing a constitutionof a power module circuit which is housed in a case.

FIG. 8 is an illustrative enlarged sectional view taken along lineVIII-VIII in FIG. 7.

FIG. 9 is a drawing which explains that a rear surface of a heatradiating plate is polished to reduce the thickness of the heatradiating plate.

FIG. 10 is an electric circuit diagram which explains an electricconstitution of a power module.

FIG. 11 is an electric circuit diagram which shows an electric circuitwhere the power module is used in an H bridge circuit.

FIG. 12 is a graph which shows a ratio of thermal resistance of thepower module on the use of a flat plate-shaped connection metal memberwith respect to thermal resistance of the power module on the use of awire in place of the flat plate-shaped connection metal member in termsof thermal resistance ratio.

FIG. 13 is a graph which shows a ratio of thermal resistance of thepower module where the rear surface of the heat radiating plate ispolished with respect to thermal resistance of the power module wherethe rear surface of the heat radiating plate is not polished in terms ofa thermal resistance ratio.

FIG. 14 is a graph which shows a ratio of thermal resistance of thepower module where the thickness of a solder layer for bonding aswitching element to a conductor layer is made thinner than a referencevalue with respect to thermal resistance of the power module where thethickness of the solder layer is equal to the reference value in termsof a thermal resistance ratio.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is an illustrative plan view which shows an internal structure ofthe power module according to one preferred embodiment of the presentinvention, showing a state in which a top plate is removed. FIG. 2 is aright side view of FIG. 1. FIG. 3 is a rear view of FIG. 1. FIG. 4 is anillustrative sectional view taken along line IV-IV in FIG. 1. FIG. 5 isan illustrative sectional view taken along line V-V in FIG. 1. FIG. 6 isan illustrative enlarged sectional view taken along line VI-VI inFIG. 1. FIG. 7 is an illustrative perspective view which explains aconstitution of a power module circuit housed in a case. FIG. 8 is anillustrative enlarged sectional view taken along line VIII-VIII in FIG.7. In FIG. 7, for clarification, wires 59, 60: 69, 70: 99, 100: 109, 110are partially illustrated (only one set for each of them).

A power module 1 includes a heat radiating plate 2, a case 3 and aplurality of terminals assembled into the case 3. The plurality ofterminals each include a first power supply terminal (in this example, apositive-electrode-side power supply terminal) P, a second power supplyterminal (in this example, a negative-electrode-side power supplyterminal) N and a first output terminal OUT1 and a second outputterminal OUT2. The plurality of terminals also each include a drainsense terminal DS, a first source sense terminal SS1, a first gateterminal G1, first and second thermistor terminals T1, T2, a secondsource sense terminal SS2 and a second gate terminal G2. The firstoutput terminal OUT1 and the second output terminal OUT2 are called an“output terminal OUT” when collectively mentioned.

For convenience of description, in the following, the +X direction, −Xdirection, +Y direction and −Y direction shown in FIG. 1 and +Zdirection and −Z direction shown in FIG. 4 may be used. The +X directionand the −X direction are two directions along a long side of the case 3(the heat radiating plate 2) having a substantially rectangular shape ina plan view, and they are simply called an “X direction” whencollectively mentioned. The +Y direction and the −Y direction are twodirections along a short side of the case 3, and they are simply calleda “Y direction” when collectively mentioned. The +Z direction and the −Zdirection are two directions along a normal of the heat radiating plate2, and these directions are simply called a “Z direction” whencollectively mentioned. When the heat radiating plate 2 is placed on ahorizontal plane, the X direction and the Y direction serve as twohorizontal directions (a first horizontal direction and secondhorizontal direction) along two straight lines (X axis and Y axis)orthogonal to each other, and the Z direction serves as a perpendiculardirection (height direction) along a perpendicular straight line (Zaxis).

The heat radiating plate 2 is a plate-shaped body with a uniformthickness having a rectangular shape in a plan view, and is made of amaterial high in heat conductivity. More specifically, the heatradiating plate 2 may be a copper plate made of copper. The copper platemay have a nickel plating layer formed on its surface. On a −Zdirection-side surface of the heat radiating plate 2, a heat sink orother cooling means are mounted whenever necessary.

The case 3 is formed in a substantially rectangular parallelepiped shapeand constituted with a resin material. It is in particular preferable touse a heat resistant resin such as PPS (polyphenylene sulfide). The case3 assumes a rectangular shape substantially similar in size to the heatradiating plate 2 in a plan view and is provided with a frame portion 4fixed to one surface of the heat radiating plate 2 (a +Z direction-sidesurface) and a top plate (not shown) fixed to the frame portion 4. Thetop plate blocks one side (a +Z direction side) of the frame portion 4and faces one surface of the heat radiating plate 2 which blocks theother side (a −Z direction side) of the frame portion 4. Accordingly,the heat radiating plate 2, the frame portion 4 and the top plate definea circuit housing space inside the case 3. In this preferred embodiment,the frame portion 4 and the plurality of terminals are formed bysimultaneous molding.

The frame portion 4 is provided with a pair of side walls 6, 7 and apair of end walls 8, 9 in which both ends of the pair of side walls 6, 7are joined to each other respectively. A recess portion 10 which is openoutward is formed each at four corners on a +Z direction-side surface ofthe frame portion 4. An outward open portion of each recess portion 10and a wall of an opposite side thereto are bent so as to protrudeinwardly. On a bottom wall of the recess portion 10, there is formed amounting through hole 11 which penetrates through the bottom wall. Atubular metal member 12 is fixed to the mounting through hole 11 in afitted state. Amounting through hole 13 (refer to FIG. 7)communicatively connected to each mounting through hole 11 is formed onthe heat radiating plate 2. The power module 1 is, by a bolt (not shown)inserted through the mounting through holes 11, 13 of the case 3 and theheat radiating plate 2, fixed to a predetermined fixing position of amounting target. The foregoing cooling means such as a heat sink may bemounted by using the mounting through holes 11, 13.

On an outer surface of the end wall 9, there is formed a power supplyterminal-use terminal block 14 having a rectangular shape long in the Ydirection in a plan view. The power supply terminal-use terminal block14 is formed integrally with the end wall 9. At a length-directioncentral portion of the surface (a +Z direction-side surface) of the endwall 9 and at a length-direction central portion of the surface of thepower supply terminal-use terminal block 14, there is formed aprotrusion portion 15 which extends in the X direction. On the surfaceof the protrusion portion 15, there are formed a plurality of grooves 16extending in the X direction. A part covering the length-directioncentral portion of the power supply terminal-use terminal block 14 andthe +Y direction side is a first power supply terminal P-use terminalblock 21. A part covering the length-direction central portion of thepower supply terminal-use terminal block 14 and the −Y direction-side isa second power supply terminal N-use terminal block 22.

On an outer surface of the end wall 8, there is formed an outputterminal-use terminal block 17 having a rectangular shape long in the Ydirection in a plan view. The output terminal-use terminal block 17 isformed integrally with the end wall 8. Ata length-direction centralportion of the surface (a +Z direction-side surface) of the end wall 8and at a length-direction central portion of the surface of the outputterminal-use terminal block 17, there is formed a protrusion portion 18which extends in the X direction. On a surface of the protrusion portion18, there are formed a plurality of grooves 19 extending in the Xdirection. A part covering the length-direction central portion of theoutput terminal-use terminal block 17 and the +Y direction-side is afirst output terminal OUT1-use terminal block 23. A part covering thelength-direction central portion of the output terminal-use terminalblock 17 and the −Y direction-side is a second output terminal OUT2-useterminal block 24.

The first power supply terminal P is arranged on a surface (+Zdirection-side surface) of a terminal block 21. The second power supplyterminal N is arranged on a surface (+Z direction-side surface) of aterminal block 22. The first output terminal OUT1 is arranged on asurface (+Z direction-side surface) of a terminal block 23. The secondoutput terminal OUT2 is arranged on a surface (+Z direction-sidesurface) of a terminal block 24.

The first power supply terminal P, the second power supply terminal N,the first output terminal OUT1 and the second output terminal OUT2 areeach prepared by cutting out a conductive plate-shaped body (forexample, a copper plate or a copper plate to which nickel plating isapplied) into a predetermined shape and giving thereto a bendingprocess, and they are electrically connected to a circuit inside thecase 3. Front end portions of the first power supply terminal P, thesecond power supply terminal N, the first output terminal OUT1 and thesecond output terminal OUT2 are led out to the terminal blocks 21, 22,23, 24 respectively. The front end portions of the first power supplyterminal P, the second power supply terminal N, the first outputterminal OUT1 and the second output terminal OUT2 are formed so as toextend along the respective surfaces of the terminal blocks 21, 22, 23,24.

On the side wall 7 which is one of the side walls, there are mounted adrain sense terminal DS, a first source sense terminal SS1, a first gateterminal G1 as well as first and second thermistor terminals T1, T2.Front end portions of these terminals DS, SS1, G1, T1, T2 protrude froma surface (+Z direction-side surface) of the side wall 7 to the outside(+Z direction) of the case 3. The drain sense terminal DS is arranged soas to be close to a −X direction-side end of the side wall 7. The firstand second thermistor terminals T1, T2 are arranged so as to be close toa +X direction-side end of the side wall 7, with an interval kept in theX direction. The first source sense terminal SS1 and the first gateterminal G1 are arranged between the −X direction-side end of the sidewall 7 and the center thereof in the length direction (the X direction),with an interval kept in the X direction.

On the side wall 6 which is the other of the side walls, there aremounted a second gate terminal G2 and a second source sense terminalSS2. Front end portions of the terminals G2, SS2 protrude from a surface(+Z direction-side surface) of the side wall 6 to the outside (+Zdirection) of the case 3. The second gate terminal G2 and the secondsource sense terminal SS2 are arranged between the center of the sidewall 6 in the length direction (the X direction) and a +X direction-sideend thereof, with an interval kept in the X direction. The drain senseterminal DS, the thermistor terminals T1, T2, the source sense terminalsSS1, DD2 and the gate terminals G1, G2 are each prepared by giving abending process to a metal rod having a rectangular shaped-cross section(for example, a rod-shaped copper body or a rod-shaped copper body towhich nickel plating is applied) and electrically connected to a circuitinside the case 3.

With reference to FIG. 1, FIG. 6, FIG. 7 and FIG. 8, the first powersupply terminal P is provided with an internal wiring connection portion31A, an upright portion 31B joined to the internal wiring connectionportion 31A, an inclined portion 31C joined to the upright portion 31B,and an external wiring connection portion 31D joined to the inclinedportion 31C. The internal wiring connection portion 31A is provided witha substantially rectangular-shaped base portion 31Aa, the four sides ofwhich are parallel to four sides of the heat radiating plate 2 in a planview, and a comb-shaped terminal 31Ab which protrudes from a −Xdirection-side end of the base portion 31As to the −X direction. Thebase portion 31Aa is constituted with a plate-shaped body extendingalong an XY plane and formed in such a shape that, of four corners, acorner on the +X direction side and also on the +Y direction side is cutoff. The comb-shaped terminal 31Ab is provided with three terminalswhich are arranged side by side in the Y direction. These terminals areeach formed in a crank shape which extends from a −X direction-side endof the base portion 31Aa in the −X direction, thereafter, bending in the−Z direction and again extending in the −X direction. The base portion31Aa is mostly embedded into the end wall 9 and the terminal block 21.

The upright portion 31B rises up in the +Z direction from a −Ydirection-side edge of the base portion 31Aa at the internal wiringconnection portion 31A. The upright portion 31B is constituted with aplate-shaped body extending along an XZ plane and formed so as to besubstantially equal in width to a length of the −Y direction-side edgeportion of the base portion 31Aa. The upright portion 31B is embeddedinto the end wall 9 and the terminal block 21. The inclined portion 31Cis joined to a +Z direction-side edge portion of the upright portion 31Band extends obliquely in the +Z direction toward the +Y direction. Theinclined portion 31C is constituted with the plate-shaped body extendingin the oblique direction and formed so as to be substantially equal inwidth to the upright portion 31B. The inclined portion 31C is embeddedinto the end wall 9 and the terminal block 21.

The external wiring connection portion 31D is joined to a +Zdirection-side edge portion of the inclined portion 31C and extends inthe +Y direction. The external wiring connection portion 31D isconstituted with a plate-shaped body along the XY plane and formed so asto be substantially equal in width to the inclined portion 31C. Theexternal wiring connection portion 31D is arranged along a surface ofthe terminal block 21. Substantially at the central portion of theexternal wiring connection portion 31D, there is formed an externalwiring connection-use insertion hole 31Da. On a −Z direction-sidesurface of the external wiring connection portion 31D, a nut 35 (referto FIG. 6) is fixed so that a screw hole is in alignment with theinsertion hole 31Da. The nut 35 is embedded into the terminal block 21.

The second power supply terminal N is formed in such a shape that givesa plane symmetry with the first power supply terminal P with respect tothe XZ plane passing through a length center of the end wall 9. Thesecond power supply terminal N is provided with an internal wiringconnection portion 32A, an upright portion 32B joined to the internalwiring connection portion 32A, an inclined portion 32C joined to theupright portion 32B, and an external wiring connection portion 32Djoined to the inclined portion 32C. The internal wiring connectionportion 32A is provided with a substantially rectangular-shaped baseportion 32Aa, the four sides of which are parallel to four sides of theheat radiating plate 2 in a plan view, and a comb-shaped terminal 32Abwhich protrudes in the −X direction from a −X direction-side end of thebase portion 32Aa. The base portion 32Aa is constituted with aplate-shaped body along the XY plane and formed in such a shape that, offour corners, a corner on the +X direction-side and also on the −Ydirection-side is cut off. The comb-shaped terminal 32Ab is providedwith three terminals which are arranged side by side in the Y direction.These terminals each have a crank shape which extends in the −Xdirection from a −X direction-side end of the base portion 32Aa and,thereafter, is bent in the −Z direction and again extends in the −Xdirection. The base portion 32Aa is mostly embedded into the end wall 9and the terminal block 22.

The upright portion 32B rises up in the +Z direction from a +Ydirection-side edge portion of the base portion 32Aa at the internalwiring connection portion 32A. The upright portion 32B is constitutedwith a plate-shaped body along the XZ plane and formed so as to besubstantially equal in width to a length of the +Y direction-side edgeportion of the base portion 32Aa. The upright portion 32B is embeddedinto the end wall 9 and the terminal block 22. The inclined portion 32Cis joined to a +Z direction-side edge portion of the upright portion 32Band extends obliquely in the +Z direction toward the −Y direction. Theinclined portion 32C is constituted with the plate-shaped body extendingobliquely and formed so as to be substantially equal in width to theupright portion 32B. The inclined portion 32C is embedded into the endwall 9 and the terminal block 22.

The external wiring connection portion 32D is joined to a +Zdirection-side edge portion of the inclined portion 32C and extends inthe −Y direction. The external wiring connection portion 32D isconstituted with a plate-shaped body along the XY plane and formed so asto be substantially equal in width to the inclined portion 32C. Theexternal wiring connection portion 32D is arranged along a surface ofthe terminal block 22. Substantially at the central portion of theexternal wiring connection portion 32D, there is formed an externalwiring connection-use insertion hole 32Da. A nut 36 (refer to FIG. 6) isfixed to a −Z direction-side surface of the external wiring connectionportion 32D so that a screw hole is in alignment with the insertion hole32Da. The nut 36 is embedded into the terminal block 22.

The upright portion 31B of the first power supply terminal P and theupright portion 32B of the second power supply terminal N are arrangedso as to face each other, with a predetermined interval kepttherebetween, thereby constituting the “plate-shaped facing portions” inthe invention as claimed in the application concerned. The uprightportion 31B and the inclined portion 31C of the first power supplyterminal P constitute a “first coupling portion” in the invention asclaimed in the application concerned. The upright portion 32B and theinclined portion 32C of the second power supply terminal N constitute a“second coupling portion” in the invention as claimed in the applicationconcerned.

The first output terminal OUT1 is formed in such a shape that gives aplane symmetry with the first power supply terminal P with respect tothe YZ plane which passes through a length center of the side wall 7.The first output terminal OUT1 is provided with an internal wiringconnection portion 33A, an upright portion 33B joined to the internalwiring connection portion 33A, an inclined portion 33C joined to theupright portion 33B, and an external wiring connection portion 33Djoined to the inclined portion 33C. The internal wiring connectionportion 33A is provided with a substantially rectangular-shaped baseportion 33Aa, the four sides of which are parallel to four sides of theheat radiating plate 2 in a plan view, and a comb-shaped terminal 33Abwhich protrudes in the +X direction from a +X direction-side end of thebase portion 33Aa. The base portion 33Aa is constituted with aplate-shaped body along the XY plane and formed in such a shaped that,of four corners, a corner on the −X direction-side and also on the +Ydirection-side is cut off. The comb-shaped terminal 33Ab is providedwith three terminals arranged side by side in the Y direction. Theseterminals are each provided with a crank shape which extends in the +Xdirection from the +X direction-side end of the base portion 33Aa,thereafter, is bent in the −Z direction and again extends in the +Xdirection. The base portion 33Aa is mostly embedded into the end wall 8and the terminal block 23.

The upright portion 33B rises up in the +Z direction from a −Ydirection-side edge portion of the base portion 33Aa at the internalwiring connection portion 33A. The upright portion 33B is constitutedwith a plate-shaped body along the XZ plane and formed so as to besubstantially equal in width to a length of the −Y direction-side edgeportion of the base portion 33Aa. The upright portion 33B is embeddedinto the end wall 8 and the terminal block 23. The inclined portion 33Cis joined to a +Z direction-side edge portion of the upright portion 33Band extends obliquely in the +Z direction toward the +Y direction. Theinclined portion 33C is constituted with the plate-shaped body extendingobliquely and formed so as to be substantially equal in width to theupright portion 33B. The inclined portion 33C is embedded into the endwall 8 and the terminal block 23.

The external wiring connection portion 33D is joined to a +Zdirection-side edge portion of the inclined portion 33C and extends inthe +Y direction. The external wiring connection portion 33D isconstituted with a plate-shaped body along the XY plane and formed so asto be substantially equal in width to the inclined portion 33C. Theexternal wiring connection portion 33D is arranged along a surface ofthe terminal block 23. There is formed an external wiring connection-useinsertion hole 33Da substantially at the central portion of the externalwiring connection portion 33D. A nut (not shown) is fixed on a −Zdirection-side surface of the external wiring connection portion 33D sothat a screw hole is in alignment with the insertion hole 33Da. The nutis embedded into the terminal block 23.

The second output terminal OUT2 is formed in such a shape that gives aplane symmetry with the first output terminal OUT1 with respect to theXZ plane which passes through a length center of the end wall 8. Thesecond output terminal OUT2 is provided with an internal wiringconnection portion 34A, an upright portion 34B joined to the internalwiring connection portion 34A, an inclined portion 34C joined to theupright portion 34B, and an external wiring connection portion 34Djoined to the inclined portion 34C. The internal wiring connectionportion 34A is provided with a substantially rectangular-shaped baseportion 34Aa, the four sides of which are parallel to four sides of theheat radiating plate 2 in a plan view, and a comb-shaped terminal 34Abwhich protrudes in the +X direction from a +X direction-side end of thebase portion 34Aa. The base portion 34Aa is constituted with aplate-shaped body along the XY plane and formed in such a shape that, offour corners, a corner on the −X direction-side and also on the −Ydirection-side is cut off. The comb-shaped terminal 34Ab is providedwith three terminals arranged side by side in the Y direction. Theseterminals are each provided with a crank shape which extends in the +Xdirection from the +X direction-side end of the base portion 34Aa,thereafter, is bent in the −Z direction and again extends in the +Xdirection. The base portion 34Aa is mostly embedded into the end wall 8and the terminal block 24.

The upright portion 34B rises up in the +Z direction from a +Ydirection-side edge portion of the base portion 34Aa at the internalwiring connection portion 34A. The upright portion 34B is constitutedwith a plate-shaped body along the XZ plane and formed so as to besubstantially equal in width to a length of the +Y direction-side edgeportion of the base portion 34Aa. The upright portion 34B is embeddedinto the end wall 8 and the terminal block 24. The inclined portion 34Cis joined to a +Z direction-side edge portion of the upright portion 34Band extends obliquely in the +Z direction toward the −Y direction. Theinclined portion 34C is constituted with the plate-shaped body extendingobliquely and formed so as to be substantially equal in width to theupright portion 34B. The inclined portion 34C is embedded into the endwall 8 and the terminal block 24.

The external wiring connection portion 34D is joined to a +Zdirection-side edge portion of the inclined portion 34C and extends inthe −Y direction. The external wiring connection portion 34D isconstituted with a plate-shaped body along the XY plane and formed so asto be substantially equal in width to the inclined portion 34C. Theexternal wiring connection portion 34D is arranged along a surface ofthe terminal block 24. There is formed an external wiring connection-useinsertion hole 34Da substantially at the central portion of the externalwiring connection portion 34D. A nut (not shown) is fixed to a −Zdirection-side surface of the external wiring connection portion 34D sothat a screw hole is in alignment with the insertion hole 34Da. The nutis embedded into the terminal block 24.

The drain sense terminal DS assumes a crank shape when viewed in the Xdirection, and an intermediate portion thereof is embedded into the sidewall 7. A base end portion of the drain sense terminal DS is arrangedinside the case 3. A front end portion of the drain sense terminal DSprotrudes in the +Z direction from a surface of the side wall 7.

The first source sense terminal SS1 assumes a crank shape when viewed inthe X direction, and an intermediate portion thereof is embedded intothe side wall 7. A base end portion of the first source sense terminalSS1 is arranged inside the case 3. A front end portion of the firstsource sense terminal SS1 protrudes in the +Z direction from a surfaceof the side wall 7.

The first gate terminal G1 assumes a crank shape when viewed in the Xdirection, and an intermediate portion thereof is embedded into the sidewall 7. A base end portion of the first gate terminal G1 is arrangedinside the case 3. A front end portion of the first gate terminal G1protrudes in the +Z direction from a surface of the side wall 7.

The thermistor terminals T1, T2 each assume a crank shape, when viewedin the X direction, and an intermediate portion thereof is embedded intothe side wall 7. Base end portions of the thermistor terminals T1, T2are each arranged inside the case 3. Front end portions of thethermistor terminals T1, T2 each protrude in the +Z direction from asurface of the side wall 7.

The second source sense terminal SS2 assumes a crank shape when viewedin the X direction, and an intermediate portion is embedded into theside wall 6. A base end portion of the second source sense terminal SS2is arranged inside the case 3. A front end portion of the second sourcesense terminal SS2 protrudes in the +Z direction from a surface of theside wall 6.

The second gate terminal G2 assumes a crank shape when viewed in the Xdirection, and an intermediate portion thereof is embedded into the sidewall 6. A base end portion of the second gate terminal G2 is arrangedinside the case 3. A front end portion of the second gate terminal G2protrudes in the +Z direction from the surface of the side wall 6.

At an area which is surrounded by the frame portion 4 on a surface (+Zdirection-side surface) of the heat radiating plate 2, a first assembly40 and a second assembly 80 are arranged side by side in the Xdirection. The first assembly 40 is arranged on the sides of the powersupply terminals P and N, and the second assembly 80 is arranged on theside of the output terminal OUT. The first assembly 40 constitutes ahalf of an upper arm (high side) circuit and a half of a lower arm (lowside) circuit. The second assembly 80 constitutes a remaining half ofthe upper arm circuit and a remaining half of the lower arm circuit. Oneof the upper arm circuit and the lower arm circuit constitutes a “firstcircuit” of the invention as claimed in the application concerned, andthe other of them constitutes a “second circuit” of the invention asclaimed in the application concerned.

The first assembly 40 includes a first insulation substrate 41, aplurality of first switching elements Tr1, a plurality of first diodeelements D11, a plurality of second switching elements Tr2, a pluralityof second diode elements Di2 and a thermistor Th.

The first insulation substrate 41 is formed in a substantiallyrectangular shape in a plan view, and four sides thereof are bonded to asurface of the heat radiating plate 2 so as to be respectively parallelto the four sides of the heat radiating plate 2. A first bondingconductor layer 42 (refer to FIG. 4) is formed on a surface (−Zdirection-side surface) of the first insulation substrate 41 on the sideof the heat radiating plate 2. The first bonding conductor layer 42 isbonded to the heat radiating plate 2 via a solder layer 52.

On a surface (+Z direction-side surface) which is an opposite side tothe heat radiating plate 2 of the first insulation substrate 41, thereare formed a plurality of upper arm circuit conductor layers, aplurality of lower arm circuit conductor layers and a plurality ofthermistor conductor layers. The plurality of upper arm circuitconductor layers each include a first element bonding conductor layer43, a first gate terminal conductor layer 44 and a first source senseterminal conductor layer 45. The plurality of lower arm circuitconductor layers each include a second element bonding-conductor layer46, an N terminal conductor layer 47, a second gate terminal conductorlayer 48, and a second source sense terminal conductor layer 49. Theplurality of thermistor conductor layers each include a first thermistorterminal conductor layer 50 and a second thermistor terminal conductorlayer 51.

In this preferred embodiment, the first insulation substrate 41 is madeof AlN (aluminum nitride). As the first insulation substrate 41, therecan be used, for example, a substrate (DBC: direct bonding copper)obtained by directly bonding copper foil on both surfaces of a ceramic.Where a DBC substrate is used as the first insulation substrate 41, theindividual conductor layers 42 to 51 can be formed from the copper foil.

The first element bonding conductor layer 43 is arranged so as to beclose to a side of a surface of the first insulation substrate 41 on the+Y direction-side and formed in a rectangular shape long in the Xdirection in a plan view. The first element bonding conductor layer 43is provided at the +X direction-side end thereof with a projectingportion extending in the −Y direction. The N terminal conductor layer 47is arranged so as to be close to a side of a surface of the firstinsulation substrate 41 on the −Y direction-side and formed in arectangular shape long in the X direction in a plan view. The N terminalconductor layer 47 is provided at the +X direction-side end thereof witha projecting portion extending toward a projecting portion of the firstelement bonding conductor layer 43. The second element bonding conductorlayer 46 is arranged at an area surrounded by the first element bondingconductor layer 43, the N terminal conductor layer 47 and the sides ofthe first insulation substrate 41 on the −X direction-side in a planview and formed in a rectangular shape which is long in the X directionin a plan view.

The first gate terminal conductor layer 44 is arranged between the firstelement bonding conductor layer 43 and a side of the first insulationsubstrate 41 on the +Y direction-side and formed in a rectangular shapelong and narrow in the X direction in a plan view. The first sourcesense terminal conductor layer 45 is arranged between the first gateterminal conductor layer 44 and a side of the first insulation substrate41 on the +Y direction-side and formed in a rectangular shape long andnarrow in the X direction in a plan view.

The first thermistor terminal conductor layer 50 is arranged on the +Xdirection-side of the first gate terminal conductor layer 44 between thefirst element bonding conductor layer 43 and a side of the firstinsulation substrate 41 on the +Y direction-side. The second thermistorterminal conductor layer 51 is arranged on the +X direction-side of thefirst source sense terminal conductor layer 45 between the first elementbonding conductor layer 43 and a side of the first insulation substrate41 on the +Y direction-side.

The second gate terminal conductor layer 48 is arranged between the Nterminal conductor layer 47 and a side of the first insulation substrate41 on the −Y direction-side and formed in a rectangular shape long andnarrow in the X direction in a plan view. The second source senseterminal conductor layer 49 is arranged between the second gate terminalconductor layer 48 and a side of the first insulation substrate 41 onthe −Y direction-side and formed in a rectangular shape long and narrowin the X direction in a plan view.

The comb-shaped terminal 31Ab of the first power supply terminal P isbonded to the +X direction-side end on a surface of the first elementbonding conductor layer 43. The comb-shaped terminal 32Ab of the secondpower supply terminal N is bonded to the +X direction-side end on asurface of the N terminal conductor layer 47. The internal wiringconnection portion 31A of the first power supply terminal P is providedwith the comb-shaped terminal 31Ab and, therefore, in bonding the firstpower supply terminal P to the first element bonding conductor layer 43,for example, a head for ultrasonic bonding is pressed onto a tip of thecomb-shaped terminal 31Ab, thus making it possible to easilyultrasonic-bond the comb-shaped terminal 31Ab to the first elementbonding conductor layer 43. Moreover, the internal wiring connectionportion 32A of the second power supply terminal N is provided with thecomb-shaped terminal 32Ab and, therefore, in bonding the second powersupply terminal N to the N terminal conductor layer 47, for example, ahead for ultrasonic bonding is pressed onto the tip of the comb-shapedterminal 32Ab, thus making it possible to easily ultrasonic-bond thecomb-shaped terminal 32Ab to the N terminal conductor layer 47.

A base end portion of the second gate terminal G2 is bonded to thesecond gate terminal conductor layer 48. A base end portion of thesecond source sense terminal SS2 is bonded to the second source senseterminal conductor layer 49. A base end portion of the first thermistorterminal T1 is bonded to the first thermistor terminal conductor layer50. A base end portion of the second thermistor terminal T2 is bonded tothe second thermistor terminal conductor layer 51. They may be bonded byultrasonic welding.

A thermistor Th is arranged on the first thermistor terminal conductorlayer 50 and the second thermistor terminal conductor layer 51 so as toextend astride them. One electrode of the thermistor Th is bonded to thefirst thermistor terminal conductor layer 50, and the other electrodethereof is bonded to the second thermistor terminal conductor layer 51.

Drain electrodes of the plurality of first switching elements Tr1 arebonded via a solder layer 53 (refer to FIG. 4) onto a surface of thefirst element bonding conductor layer 43, and cathode electrodes of theplurality of first diode elements D11 are bonded via a solder layer 54.In this preferred embodiment, the solder layers 53, 54 are made ofSn—Ag—Cu-based solder. In this preferred embodiment, these solder layers53, 54 are made thinner in thickness (for example, 0.08 mm) than athickness of general solder (for example, 0.12 mm). Each of the firstswitching elements Tr1 is provided with a source electrode and a gateelectrode on a surface which is an opposite side to a surface bonded tothe first element bonding conductor layer 43. Each of the first diodeelements Di1 is provided with an anode electrode on a surface which isan opposite side to a surface bonded to the first element bondingconductor layer 43.

Five first diode elements Di1 are arranged side by side, with aninterval kept, in the X direction, so as to be close to a side of asurface of the first element bonding conductor layer 43 on the +Ydirection-side. Five first switching elements Tr1 are arranged side byside, with an interval kept, in the X direction between a side of thefirst element bonding conductor layer 43 on the −Y direction-side andthe five first diode elements Di1. The five first switching elements Tr1are positionally in alignment with the five first diode elements Di1with respect to the Y direction.

The first switching elements Tr1 and the first diode elements Di1 whichare positionally in alignment with each other in the Y direction areconnected to the second element bonding conductor layer 46 by a firstconnection metal member 55 extending substantially in the Y direction ina plan view. The first connection metal member 55 is formed in arectangular shape long in the Y direction in a plan view. The firstconnection metal member 55 is prepared by giving a bending process to aconductive plate-shaped body (for example, a copper plate or a copper towhich plate nickel plating is applied). The first connection metalmember 55 is constituted with a bonding portion 55 a (refer to FIG. 4)which is bonded to the second element bonding conductor layer 46, anupright portion 55 b which is joined to the bonding portion 55 a and atransverse portion 55 c which is joined to the upright portion 55 b.

The bonding portion 55 a is bonded to an area close to a +Ydirection-side edge of the second element bonding conductor layer 46 viaa solder layer 56 and formed in a rectangular shape which extends in theX direction in a plan view. The upright portion 55 b rises up in the +Zdirection from a +Y direction-side edge portion of the bonding portion55 a. The upright portion 55 b is constituted with a plate-shaped bodyalong the XZ plane and formed so as to be substantially equal in widthto the bonding portion 55 a. The transverse portion 55 c is joined to a+Z direction-side edge portion of the upright portion 55 b and extendsin the +Y direction. A length intermediate portion and a front endportion of the transverse portion 55 c are respectively arranged abovethe first switching elements Tr1 and the first diode elements Di1. Thetransverse portion 55 c is constituted with a plate-shaped body which isparallel to a principal surface of the heat radiating plate 2 and formedso as to be substantially equal in width to the upright portion 55 b. Afront end portion (+Y direction-side end portion) of the transverseportion 55 c is bonded to an anode electrode of the first diode elementDi1 via a solder layer 57, and a length intermediate portion of thetransverse portion 55 c is bonded to a source electrode of the firstswitching element Tr1 via a solder layer 58. Accordingly, the anodeelectrode of the first diode element Di1 and the source electrode of thefirst switching element Tr1 are electrically connected to the secondelement bonding conductor layer 46 via the first connection metal member55.

A width (length in the X direction) of the first connection metal member55 is shorter than a width (length in the X direction) of the firstswitching element Tr1. A +X direction-side edge of the transverseportion 55 c of the first connection metal member 55 is positionally inalignment with a +X direction-side edge of the first switching elementTr1 and that of the first diode element Di1 in a plan view. A −Xdirection-side edge of the transverse portion 55 c of the firstconnection metal member 55 is positioned closer to the +X direction-sidethan the −X direction-side edge of the first switching element Tr1 andthat of the first diode element Di1 in a plan view. Accordingly, of the+Z direction-side surface of the first switching element Tr1 and that ofthe first diode element Di1, an area close to the −X direction-side edgeis exposed inside the case 3.

A gate electrode of each first switching element Tr1 is connected to thefirst gate terminal conductor layer 44 by a wire 59. A source electrodeof each first switching element Tr1 is connected to the first sourcesense terminal conductor layer 45 by a wire 60.

Drain electrodes of the plurality of second switching elements Tr2 arebonded to a surface of the second element bonding conductor layer 46 viaa solder layer 61 (refer to FIG. 4) and also cathode electrodes of theplurality of second diode elements Di2 are bonded thereto via a solderlayer 62. In this preferred embodiment, these solder layers 61, 62 aremade of Sn—Ag—Cu-based solder. In this preferred embodiment, thethickness of each of the solder layers 61, 62 is made thinner (forexample, 0.08 mm) than a thickness of general solder (for example, 0.12mm). Each of the second switching elements Tr2 is provided with a sourceelectrode and a gate electrode on a surface which is an opposite side toa surface bonded to the second element bonding conductor layer 46. Eachof the second diode elements Di2 is provided with an anode electrode ona surface which is an opposite side to a surface bonded to the secondelement bonding conductor layer 46.

Five second switching elements Tr2 are arranged side by side, with aninterval kept, in the X direction, so as to be close to a −Ydirection-side on a surface of the second element bonding conductorlayer 46. Moreover, five second diode elements Di2 are arranged side byside, with an interval kept, in the X direction between a side of thesecond element bonding conductor layer 46 on the +Y direction-side andthe five second switching elements Tr2. The five second diode elementsDi2 are positionally in alignment with the five second switchingelements Tr2 with respect to the Y direction. Further, the five seconddiode elements Di2 are also positionally in alignment with the fivefirst switching elements Tr1 with respect to the Y direction.

The second switching elements Tr2 and the second diode elements Di2positionally in alignment with each other in the Y direction areconnected to the N terminal conductor layer 47 by a second connectionmetal member 65 extending substantially in the Y direction in a planview. The second connection metal member 65 is prepared by giving abending process to a conductive plate-shaped body (for example, a copperplate or a copper plate to which nickel plating is applied). The secondconnection metal member 65 is constituted with a bonding portion 65 a(refer to FIG. 4) bonded to the N terminal conductor layer 47, anupright portion 65 b joined to the bonding portion 65 a and a transverseportion 65 c joined to the upright portion 65 b.

The bonding portion 65 a is bonded to an area close to a +Ydirection-side edge of the N terminal conductor layer 47 via a solderlayer 66 and formed in a rectangular shape extending in the X directionin a plan view. The upright portion 65 b rises up in the +Z directionfrom a +Y direction-side edge portion of the bonding portion 65 a. Theupright portion 65 b is constituted with a plate-shaped body along theXZ plane and formed so as to be substantially equal in width to thebonding portion 65 a. The transverse portion 65 c is joined to a +Zdirection-side edge portion of the upright portion 65 b and extends inthe +Y direction. A length intermediate portion and a front end portionof the transverse portion 65 c are respectively arranged above thesecond switching elements Tr2 and the second diode elements Di2. Thetransverse portion 65 c is constituted with a plate-shaped body which isparallel to a principal surface of the heat radiating plate 2 and formedso as to be substantially equal in width to the upright portion 65 b. Afront end portion (+Y direction-side end portion) of the transverseportion 65 c is bonded to an anode electrode of the second diode elementDi2 via a solder layer 67, and a length intermediate portion of thetransverse portion 65 c is bonded to a source electrode of the secondswitching element Tr2 via a solder layer 68. Accordingly, the anodeelectrode of the second diode element Di2 and the source electrode ofthe second switching element Tr2 are electrically connected to the Nterminal conductor layer 47 via the second connection metal member 65.

A width (length in the X direction) of the second connection metalmember 65 is shorter than a width (length in the X direction) of thesecond switching element Tr2. A +X direction-side edge of the transverseportion 65 c of the second connection metal member 65 is positionally inalignment with a +X direction-side edge of the second switching elementTr2 and that of the second diode element Di2 in a plan view. A −Xdirection-side edge of the transverse portion 65C of the secondconnection metal member 65 is positioned closer to the +X direction-sidethan the −X direction-side edge of the second switching element Tr2 andthat of the second diode element Di2 in a plan view. Accordingly, of the+Z direction-side surface of the second switching element Tr2 and thatof the second diode element Di2, an area close to the −X direction-sideedge is exposed inside the case 3.

A gate electrode of each second switching element Tr2 is connected tothe second gate terminal conductor layer 48 via a wire 69. A sourceelectrode of each second switching element Tr2 is connected to thesecond source sense terminal conductor layer 49 via a wire 70.

The second assembly 80 includes a second insulation substrate 81, aplurality of third switching elements Tr3, a plurality of third diodeelements Di3, a plurality of fourth switching elements Tr4 and aplurality of fourth diode elements Di4.

The first switching elements Tr1 of the first assembly 40 and/or thethird switching elements Tr3 of the second assembly 80 constitute a“first switching element” of the invention as claimed in the applicationconcerned. The second switching elements Tr2 of the first assembly 40and/or the fourth switching elements Tr4 of the second assembly 80constitute a “second switching element” of the invention as claimed inthe application concerned. The first diode elements Di1 of the firstassembly 40 and/or the third diode elements Di3 of the second assembly80 constitute a “first diode element” of the invention as claimed in theapplication concerned. The second diode elements Di2 of the firstassembly 40 and/or the fourth diode elements Di4 of the second assembly80 constitute a “second diode element” of the invention as claimed inthe application concerned.

The second insulation substrate 81 is formed in a substantiallyrectangular shape in a plan view and bonded to a surface of the heatradiating plate 2 so that the four sides thereof are parallelrespectively to four sides of the heat radiating plate 2. A secondbonding conductor layer 82 (refer to FIG. 5) is formed on a surface (−Zdirection-side surface) of the second insulation substrate 81 on theside of the heat radiating plate 2. The second bonding conductor layer82 is bonded to the heat radiating plate 2 via a solder layer 90.

A plurality of upper arm circuit conductor layers and a plurality oflower arm circuit conductor layers are formed on a surface (+Zdirection-side surface) which is an opposite side to the heat radiatingplate 2 of the second insulation substrate 81. The plurality of upperarm circuit conductor layers each include a third element bondingconductor layer 83, a third gate terminal conductor layer 84 and a thirdsource sense terminal conductor layer 85. The plurality of lower armcircuit conductor layers each include a fourth element bonding conductorlayer 86, a source conductor layer 87, a fourth gate terminal conductorlayer 88 and a fourth source sense terminal conductor layer 89.

The first element bonding conductor layer 43 of the first assembly 40and/or the third element bonding conductor layer 83 of the secondassembly 80 constitute a “first element bonding conductor layer” of theinvention as claimed in the application concerned. The second elementbonding conductor layer 46 of the first assembly 40 and/or the fourthelement bonding conductor layer 86 of the second assembly 80 constitutea “second element bonding conductor layer” of the invention as claimedin the application concerned. The N terminal conductor layer 47 of thefirst assembly 40 and/or the source conductor layer 87 of the secondassembly 80 constitute a “second power supply terminal conductor layer”of the invention as claimed in the application concerned.

In this preferred embodiment, the second insulation substrate 81 is madeof AlN (aluminum nitride). As the second insulation substrate 81, therecan be used, for example, a substrate (DBC: direct bonding copper)obtained by directly bonding copper foil to both surfaces of a ceramic.Where a DBC substrate is used as the second insulation substrate 81, theindividual conductor layers 82 to 89 can be formed from the copper foil.

The third element bonding conductor layer 83 is arranged so as to beclose to a side of a surface of the second insulation substrate 81 onthe +Y direction-side and formed in a rectangular shape which is longerin the X direction in a plan view. The third element bonding conductorlayer 83 is provided at the −X direction-side end with a projectingportion extending in the +Y direction. Abase end portion of the drainsense terminal DS is bonded to the projecting portion.

The source conductor layer 87 is arranged so as to be close to a side ofa surface of the second insulation substrate 81 on the −Y direction-sideand formed in a rectangular shape which is long in the X direction in aplan view. The fourth element bonding conductor layer 86 is formed in aT-letter shape in a plan view. The fourth element bonding conductorlayer 86 is arranged between the third element bonding conductor layer83 and the source conductor layer 87 and also includes arectangular-shaped element bonding portion 86 a longer in the Xdirection in a plan view and an output terminal bonding portion 86 bextending along a side of the second insulation substrate 81 on the −Xdirection-side. A −X direction-side end of the element bonding portion86 a is coupled to a length central portion of the output terminalbonding portion 86 b.

The third gate terminal conductor layer 84 is arranged between the thirdelement bonding conductor layer 83 and a side of the second insulationsubstrate 81 on the +Y direction-side and formed in a rectangular shapewhich is long and narrow in the X direction in a plan view. The thirdsource sense terminal conductor layer 85 is arranged between the thirdgate terminal conductor layer 84 and a side of the second insulationsubstrate 81 on the +Y direction-side and formed in a rectangular shapewhich is long and narrow in the X direction in a plan view.

The fourth gate terminal conductor layer 88 is arranged between thesource conductor layer 87 and a side of the second insulation substrate81 on the −Y direction-side and formed in a rectangular shape which islong and narrow in the X direction in a plan view. The fourth sourcesense terminal conductor layer 89 is arranged between the fourth gateterminal conductor layer 88 and a side of the second insulationsubstrate 81 on the −Y direction-side and formed in a rectangular shapewhich is long and narrow in the X direction in a plan view.

The comb-shaped terminal 33Ab of the first output terminal OUT1 and thecomb-shaped terminal 34Ab of the second output terminal OUT2 are bondedto a surface of the output terminal bonding portion 86 b on the fourthelement bonding conductor layer 86. The internal wiring connectionportion 33A of the first output terminal OUT1 is provided with thecomb-shaped terminal 33Ab and, therefore, in bonding the first outputterminal OUT1 to the output terminal bonding portion 86 b, for example,a head for ultrasonic bonding is pressed onto the tip of the comb-shapedterminal 33Ab, thus making it possible to easily ultrasonic-bond thecomb-shaped terminal 33Ab to the output terminal bonding portion 86 b.Moreover, the internal wiring connection portion 34A of the secondoutput terminal OUT2 is provided with the comb-shaped terminal 34Ab and,therefore, in bonding the second output terminal OUT2 to the outputterminal bonding portion 86 b, for example, a head for ultrasonicbonding is pressed onto the tip of the comb-shaped terminal 34Ab, thusmaking it possible to easily ultrasonic-bond the comb-shaped terminal34Ab to the output terminal bonding portion 86 b.

A base end portion of the first gate terminal G1 is bonded to the thirdgate terminal conductor layer 84. A base end portion of the first sourcesense terminal SS1 is bonded to the third source sense terminalconductor layer 85. They may be bonded by ultrasonic welding.

Drain electrodes of the plurality of third switching elements Tr3 arebonded to a surface of the third element bonding conductor layer 83 viaa solder layer 91 (refer to FIG. 5) and also cathode electrodes of theplurality of third diode elements Di3 are bonded thereto via a solderlayer 92. The foregoing solder layer 53 and/or the solder layer 91constitute a “first solder layer” of the invention as claimed in theapplication concerned. The foregoing solder layer 54 and/or the solderlayer 92 constitute a “third solder layer” of the invention as claimedin the application concerned. In this preferred embodiment, these solderlayers 91, 92 are made of Sn—Ag—Cu-based solder. In this preferredembodiment, a thickness of each of the solder layers 91, 92 is madethinner (for example, 0.08 mm) than a thickness of general solder (forexample, 0.12 mm). Each of the third switching elements Tr3 is providedwith a source electrode and a gate electrode on a surface which is anopposite side to a surface bonded to the third element bonding conductorlayer 83. Each of the third diode elements Di3 is provided with an anodeelectrode on a surface which is an opposite side to a surface bonded tothe third element bonding conductor layer 83.

Five third diode elements Di3 are arranged side by side, with aninterval kept, in the X direction so as to be close to a side of asurface of the third element bonding conductor layer 83 on the +Ydirection-side. Moreover, five third switching elements Tr3 are arrangedside by side, with an interval kept, in the X direction between a sideof the third element bonding conductor layer 83 on the −Y direction-sideand the five third diode elements Di3. The five third switching elementsTr3 are positionally in alignment with the five third diode elements Di3with respect to the Y direction.

The third switching elements Tr3 and the third diode elements Di3positionally in alignment with each other in the Y direction areconnected to the fourth element bonding conductor layer 86 by a thirdconnection metal member 95 extending substantially in the Y direction ina plan view. The third connection metal member 95 is prepared by givinga bending process to a conductive plate-shaped body (for example, acopper plate or a copper plate to which nickel plating is applied). Thethird connection metal member 95 is constituted with a bonding portion95 a (refer to FIG. 5) bonded to the fourth element bonding conductorlayer 86, an upright portion 95 b joined to the bonding portion 95 a anda transverse portion 95 c joined to the upright portion 95 b.

The bonding portion 95 a is bonded to an area close to a +Ydirection-side edge of the fourth element bonding conductor layer 86 viaa solder layer 96 and formed in a rectangular shape extending in the Xdirection in a plan view. The upright portion 95 b rises up in the +Zdirection from a +Y direction-side edge portion of the bonding portion95 a. The upright portion 95 b is constituted with a plate-shaped bodyalong the XZ plane and formed so as to be substantially equal in widthto the bonding portion 95 a. The transverse portion 95 c is joined to a+Z direction-side edge portion of the upright portion 95 b and extendsin the +Y direction. A length intermediate portion and a front endportion of the transverse portion 95 c are arranged respectively abovethe third switching elements Tr3 and the third diode elements Di3. Thetransverse portion 95 c is constituted with a plate-shaped body parallelto a principal surface of the heat radiating plate 2 and formed so as tobe substantially equal in width to the upright portion 95 b. A front endportion (+Y direction-side end portion) of the transverse portion 95 cis bonded to an anode electrode of the third diode element Di3 via asolder layer 97 and a length intermediate portion of the transverseportion 95 c is bonded to a source electrode of the third switchingelement Tr3 via a solder layer 98. Accordingly, the anode electrode ofthe third diode element Di3 and the source electrode of the thirdswitching element Tr3 are electrically connected to the fourth elementbonding conductor layer 86 via the third connection metal member 95.

A width (length in the X direction) of the third connection metal member95 is shorter than a width (length in the X direction) of the thirdswitching element Tr3. The −X direction-side edge of the transverseportion 95 c of the third connection metal member 95 is positionally inalignment with the −X direction-side edge of the third switching elementTr3 and that of the third diode element Di3 in a plan view. The +Xdirection-side edge of the transverse portion 95 c of the thirdconnection metal member 95 is positioned so as to be closer to the −Xdirection-side than the +X direction-side edge of the third switchingelement Tr3 and that of the third diode element Di3 in a plan view.Accordingly, of the +Z direction-side surface of the third switchingelement Tr3 and that of the third diode element Di3, an area close tothe +X direction-side edge is exposed inside the case 3.

A gate electrode of each of the third switching elements Tr3 isconnected to the third gate terminal conductor layer 84 by a wire 99. Asource electrode of each of the third switching elements Tr3 isconnected to the third source sense terminal conductor layer 85 by awire 100.

Drain electrodes of the plurality of fourth switching elements Tr4 arebonded to a surface of the fourth element bonding conductor layer 86 viaa solder layer 101 (refer to FIG. 5) and also cathode electrodes of theplurality of fourth diode elements Di4 are bonded thereto via a solderlayer 102. The foregoing solder layer 61 and/or the solder layer 101constitute a “second solder layer” of the invention as claimed in theapplication concerned. The foregoing solder layer 62 and/or the solderlayer 102 constitute a “fourth solder layer” of the invention as claimedin the application concerned. In this preferred embodiment, these solderlayers 101 and 102 are made of Sn—Ag—Cu-based solder. In this preferredembodiment, a thickness of each of the solder layers 101, 102 is madethinner (for example, 0.08 mm) than a thickness of general solder (forexample, 0.12 mm). Each of the fourth switching elements Tr4 is providedwith a source electrode and a gate electrode on a surface which is anopposite side to a surface bonded to the fourth element bondingconductor layer 86. Each of the fourth diode elements Di4 is providedwith an anode electrode on a surface which is an opposite side to asurface bonded to the fourth element bonding conductor layer 86.

Five fourth switching elements Tr4 are arranged side by side, with aninterval kept, in the X direction so as to be close to the −Ydirection-side on a surface of the fourth element bonding conductorlayer 86. Moreover, five fourth diode elements Di4 are arranged side byside, with an interval kept, in the X direction between a side of thefourth element bonding conductor layer 86 on the +Y direction-side andthe five fourth switching elements Tr4. The five fourth diode elementsDi4 are positionally in alignment with the five fourth switchingelements Tr4 with respect to the Y direction. Further, the five fourthdiode elements Di4 are also positionally in alignment with the fivethird switching elements Tr3 with respect to the Y direction.

The fourth switching elements Tr4 and the fourth diode elements Di4positionally in alignment with each other in the Y direction areconnected to the source conductor layer by a fourth connection metalmember 105 extending substantially in the Y direction in a plan view.The fourth connection metal member 105 is prepared by giving a bendingprocess to a conductive plate-shaped body (for example, a copper plateor a copper plate to which nickel plating is applied). The fourthconnection metal member 105 is constituted with a bonding portion 105 a(refer to FIG. 5) bonded to the source conductor layer 87, an uprightportion 105 b joined to the bonding portion 105 a and a transverseportion 105 c joined to the upright portion 105 b.

The bonding portion 105 a is bonded to an area close to the +Ydirection-side edge of the source conductor layer 87 via a solder layer106 and formed in a rectangular shape extending in the X direction in aplan view. The upright portion 105 b rises up in the +Z direction from a+Y direction-side edge portion of the bonding portion 105 a. The uprightportion 105 b is constituted with a plate-shaped body along the XZ planeand formed so as to be substantially equal in width to the bondingportion 105 a. The transverse portion 105 c is joined to a +Zdirection-side edge portion of the upright portion 105 b and extends inthe +Y direction. A length intermediate portion and a front end portionof the transverse portion 105 c are arranged respectively above thefourth switching elements Tr4 and the fourth diode elements Di4. Thetransverse portion 105 c is constituted with a plate-shaped bodyparallel to a principal surface of the heat radiating plate 2 and formedso as to be substantially equal in width to the upright portion 105 b. Afront end portion (+Y direction-side end portion) of the transverseportion 105 c is bonded to an anode electrode of the fourth diodeelement Di4 via a solder layer 107, and a length intermediate portion ofthe transverse portion 105 c is bonded to a source electrode of thefourth switching element Tr4 via a solder layer 108. Accordingly, theanode electrode of the fourth diode element Di4 and the source electrodeof the fourth switching element Tr4 are electrically connected to thesource conductor layer 87 via the fourth connection metal member 105.

A width (length in the X direction) of the fourth connection metalmember 105 is shorter than a width (length in the X direction) of thefourth switching element Tr4. A −X direction-side edge of the transverseportion 105 c of the fourth connection metal member 105 is positionallyin alignment with a −X direction-side edge of the fourth switchingelement Tr4 and that of the fourth diode element Di4 in a plan view. A+X direction-side edge of the transverse portion 105 c of the fourthconnection metal member 105 is positioned so as to be closer to the −Xdirection-side than the +X direction-side edge of the fourth switchingelement Tr4 and that of the fourth diode element Di4 in a plan view.Accordingly, of a +Z direction-side surface of the fourth switchingelement Tr4 and that of the fourth diode element Di4, an area closer tothe +X direction-side edge is exposed inside the case 3.

A gate electrode of each of the fourth switching elements Tr4 isconnected to the fourth gate terminal conductor layer 88 by a wire 109.A source electrode of each of the fourth switching elements Tr4 isconnected to the fourth source sense terminal conductor layer 89 by awire 110.

The third element bonding conductor layer 83 of the second assembly 80is connected to the first element bonding conductor layer 43 of thefirst assembly 40 by a first conductor layer connecting member 111. Thefirst conductor layer connecting member 111 is constituted with aconductive plate-shaped body which is H-shaped in a plan view. The firstconductor layer connecting member 111 is constituted with a pair ofrectangular portions extending astride the third element bondingconductor layer 83 and the first element bonding conductor layer 43 aswell as a coupling portion which couples length central portions ofthese rectangular portions. One end portion and the other end portion ofthe pair of rectangular portions each constitute a comb-shaped terminal.The first element bonding conductor layer 43 is connected to the thirdelement bonding conductor layer 83 by the first conductor layerconnecting member 111 made of a plate-shaped body, by which lowerinductance can be attained as compared with a case where they areconnected by a wire.

Further, the first conductor layer connecting member 111 is providedwith the comb-shaped terminal and, therefore, in bonding, for example,the first conductor layer connecting member 111 to the first elementbonding-conductor layer 43, a head for ultrasonic bonding is pressedonto the comb-shaped terminal of the first conductor layer connectingmember 111 on the +X direction-side. Thereby, it is possible to easilyultrasonic-bond the first conductor layer connecting member 111 to thefirst element bonding conductor layer 43.

The fourth element bonding conductor layer 86 of the second assembly 80is connected to the second element bonding conductor layer 46 of thefirst assembly 40 by a second conductor layer connecting member 112. Thesecond conductor layer connecting member 112 is constituted with aconductive plate-shaped body which is H-shaped in a plan view. Thesecond conductor layer connecting member 112 is constituted with a pairof rectangular portions extending astride the fourth element bondingconductor layer 86 and the second element bonding conductor layer 46 aswell as a coupling portion which couples length central portions ofthese rectangular portions. One end portion and the other end portion ofthe pair of rectangular portions each constitute a comb-shaped terminal.The second element bonding conductor layer 46 is connected to the fourthelement bonding conductor layer 86 by the second conductor layerconnecting member 112 made of a plate-shaped body, by which lowerinductance can be attained as compared with a case where they areconnected by a wire.

Further, the second conductor layer connecting member 112 is providedwith the comb-shaped terminal and, therefore, in bonding, for example,the second conductor layer connecting member 112 to the second elementbonding conductor layer 46, a head for ultrasonic bonding is pressedonto the comb-shaped terminal of the second conductor layer connectingmember 112 on the +X direction-side. Thereby, it is possible to easilyultrasonic-bond the second conductor layer connecting member 112 to thesecond element bonding conductor layer 46.

The source conductor layer 87 of the second assembly 80 is connected tothe N terminal conductor layer 47 of the first assembly 40 by a thirdconductor layer connecting member 113. The third conductor layerconnecting member 113 is constituted with a conductive plate-shaped bodywhich is H-shaped in a plan view. The third conductor layer connectingmember 113 is constituted with a pair of rectangular portions extendingastride the source conductor layer 87 and the N terminal conductor layer47 as well as a coupling portion which couples length central portionsof these rectangular portions. One end portion and the other end portionof the pair of rectangular portions each constitute a comb-shapedterminal. The N terminal conductor layer 47 is connected to the sourceconductor layer 87 by the third conductor layer connecting member 113made of a plate-shaped body, by which lower inductance can be attainedas compared with a case where they are connected by a wire. Further, thethird conductor layer connecting member 113 is provided with thecomb-shaped terminal and, therefore, in bonding, for example, the thirdconductor layer connecting member 113 to the N terminal conductor layer47, a head for ultrasonic bonding is pressed onto the comb-shapedterminal of the third conductor layer connecting member 113 on the +Xdirection-side. Thereby, it is possible to easily ultrasonic-bond thethird conductor layer connecting member 113 to the N terminal conductorlayer 47.

The third gate terminal conductor layer 84 of the second assembly 80 isconnected to the first gate terminal conductor layer 44 of the firstassembly 40 via a wire 114. The third source sense terminal conductorlayer 85 of the second assembly 80 is connected to the first sourcesense terminal conductor layer 45 of the first assembly 40 via a wire115.

The fourth gate terminal conductor layer 88 of the second assembly 80 isconnected to the second gate terminal conductor layer 48 of the firstassembly 40 via a wire 116. The fourth source sense terminal conductorlayer 89 of the second assembly 80 is connected to the second sourcesense terminal conductor layer 49 of the first assembly 40 via a wire117.

Where the first assembly 40 and the second assembly 80 are assembled tothe heat radiating plate 2, the heat radiating plate 2 is warped so thatthe central portion thereof is protruded as shown at an upper side ofFIG. 9. In this preferred embodiment, after the first assembly 40 andthe second assembly 80 are assembled to the heat radiating plate 2, alower surface (surface in the −Z direction) of the heat radiating plate2 is polished until it gives a flat surface as indicated by a doubledotted and dashed line 120. Accordingly, as shown at a lower side ofFIG. 9, there is provided a heat radiating plate 2 which is thinner thanthe heat radiating plate 2 shown at the upper side of FIG. 9. In thispreferred embodiment, a thickness t of a peripheral edge portion of theheat radiating plate 2 shown at the upper side of FIG. 9 is, forexample, about 4 mm, while a thickness t of a peripheral edge portion ofthe heat radiating plate 2 shown at the lower side of FIG. 9 is, forexample, about 3.5 mm.

FIG. 10 is an electric circuit diagram for explaining an electricconstitution of the power module 1. In FIG. 10, two output terminalsOUT1 and OUT2 are shown as one output terminal OUT.

The plurality of first switching elements Tr1 and the plurality of firstdiode elements Di1 installed at the first assembly 40 as well as theplurality of third switching elements Tr3 and the plurality of thirddiode elements Di3 installed at the second assembly 80 are connected inparallel between the first power supply terminal P and the outputterminal OUT, thereby forming an upper arm circuit (high side circuit)301. The plurality of second switching elements Tr2 and the plurality ofsecond diode elements Di2 installed at the first assembly 40 as well asthe plurality of fourth switching elements Tr4 and the plurality offourth diode elements Di4 installed at the second assembly 80 areconnected between the output terminal OUT and the second power supplyterminal N, thereby forming a lower arm circuit (low-side circuit) 302.

The upper arm circuit 301 and the lower arm circuit 302 are connected inseries between the first power supply terminal P and the second powersupply terminal N, and the output terminal OUT is connected to aconnecting point 303 between the upper arm circuit 301 and the lower armcircuit 302. In this way, a half bridge circuit is constituted. The halfbridge circuit can be used as a single-phase bridge circuit. Further,the plural number (for example, three) of half bridge circuits (powermodule 1) are connected to a power supply in parallel, by which aplural-phase (for example, three-phase) bridge circuit can beconstituted.

The first to fourth switching elements Tr1 to Tr4 are, in this preferredembodiment, constituted with N-channel DMOS (double-diffused metal oxidesemiconductor) field-effect transistors. Particularly, in this preferredembodiment, the first to fourth switching elements Tr1 to Tr4 arehigh-speed switching MOSFETs (SiC-DMOS) constituted with SiCsemiconductor devices.

Moreover, the first to fourth diode elements Di1 to Di4 are, in thispreferred embodiment, constituted with Schottky barrier diodes (SBD).Particularly, in this preferred embodiment, the first to fourth diodeelements Di1 to Di4 are constituted with SiC semiconductor devices(SiC-SBDs).

The first diode elements Di1 are connected in parallel to the individualfirst switching elements Tr1. The third diode elements Di3 are connectedin parallel to the individual third switching elements Tr3. A drain ofeach of the first switching elements Tr1 and that of each of the thirdswitching elements Tr3 as well as a cathode of each of the first diodeelements Di1 and that of each of the third diode elements Di3 areconnected to the first power supply terminal P.

Anodes of the plurality of first diode elements Di1 are connected tosources of the corresponding first switching elements Tr1, and thesources of the first switching elements Tr1 are connected to the outputterminal OUT. Similarly, anodes of the plurality of third diode elementsDi3 are connected to sources of the corresponding third switchingelements Tr3, and the sources of the third switching elements Tr3 areconnected to the output terminal OUT.

Gates of the plurality of first switching elements Tr1 and those of theplurality of third switching elements Tr3 are connected to the firstgate terminal G1. The sources of the plurality of first switchingelements Tr1 and those of the plurality of third switching elements Tr3are connected to the first source sense terminal SS1 as well. Drains ofthe plurality of first switching elements Tr1 and those of the pluralityof third switching elements Tr3 are connected to the drain senseterminal DS as well.

The second diode elements Di2 are connected in parallel to theindividual second switching elements Tr2. The fourth diode elements Di4are connected in parallel to the individual fourth switching elementsTr4. A drain of each of the second switching elements Tr2 and that ofeach of the fourth switching elements Tr4 as well as a cathode of eachof the second diode elements Di2 and that of each of the fourth diodeelements Di4 are connected to the output terminal OUT.

Anodes of the plurality of second diode elements Di2 are connected tosources of the corresponding second switching elements Tr2, and thesources of the second switching elements Tr2 are connected to the secondpower supply terminal N. Similarly, anodes of the plurality of fourthdiode elements Di4 are connected to sources of the corresponding fourthswitching elements Tr4, and the sources of the fourth switching elementsTr4 are connected to the second power supply terminal N.

Gates of the plurality of second switching elements Tr2 and those of theplurality of fourth switching elements Tr4 are connected to the secondgate terminal G2. The sources of the plurality of second switchingelements Tr2 and those of the plurality of fourth switching elements Tr4are also connected to the second source sense terminal SS2.

FIG. 11 shows an electric circuit in which the power module 1 is used atan H bridge circuit. In the H bridge circuit, two power modules 1 areconnected in parallel to a power supply 201. One of the power modules 1is called a first power module 1A, and the other of the power modules 1is called a second power module 1B. In FIG. 11, for convenience ofdescription, the plurality of first and third switching elements Tr1,Tr3 and the plurality of first and third diode elements Di1, Di3 whichconstitute the upper arm circuit are expressed respectively by one firstswitching element Tr1 and one first diode element Di1. Similarly, theplurality of second and fourth switching elements Tr2, Tr4 and theplurality of second and fourth diode elements Di2, Di4 which constitutethe lower arm circuit are expressed respectively by one second switchingelement Tr2 and one second diode element Di2. An inductive load 202 suchas a motor is connected between the output terminals OUT of the twopower modules 1A and 1B.

In the above-described H bridge circuit, for example, the firstswitching elements Tr1 of the first power module 1A and the secondswitching elements Tr2 of the second power module 1B are kept in aconductive state. Thereafter, these switching elements Tr1, Tr2 are keptin a cutoff state. Then, the second switching elements Tr2 of the firstpower module 1A and the first switching elements Tr1 of the second powermodule 1B are kept in a conductive state. Thereafter, these switchingelements Tr1, Tr2 are kept in a cutoff state. Then, the first switchingelements Tr1 of the first power module 1A and the second switchingelements Tr2 of the second power module 1B are kept in a conductivestate. These motions are repeated, by which the load 202 is AC driven.

During a transition period when the first switching elements Tr1 insidethe first power module 1A are switched from a conductive state to acutoff state and the second switching elements Tr2 are switched from acutoff state to a conductive state, as shown by the arrows in FIG. 11,in the first power module 1A, a current flows from the first powersupply terminal P through the first switching elements Tr1 to the outputterminal OUT and flows from the output terminal OUT through the secondswitching elements Tr2 to the second power supply terminal N. Alsoduring a transition period when the second switching elements Tr2 insidethe first power module 1A are switched from a conductive state to acutoff state and the first switching elements Tr1 are switched from acutoff state to a conductive state, in the first power module 1A, acurrent flows from the first power supply terminal P through the firstswitching element Tr1 to the output terminal OUT and flows from theoutput terminal OUT through the second switching element Tr2 to thesecond power supply terminal N.

With reference to FIG. 7 and FIG. 8, during the transition period, acurrent flows through the upright portion 31B of the first power supplyterminal P at the first power module 1A mainly in the −Z direction (adirection from the side of the external wiring connection portion 31D tothe side of the internal wiring connection portion 31A). On the otherhand, a current flows through the upright portion 32B of the secondpower supply terminal N at the first power module 1A mainly in the +Zdirection (a direction from the side of the internal wiring connectionportion 32A to the side of the external wiring connection portion 32D).

The upright portion 31B of the first power supply terminal P throughwhich a current flows in the −Z direction and the upright portion 32B ofthe second power supply terminal N through which a current flows in the+Z direction face each other and also come close to each other.Accordingly, self-inductance of the first power supply terminal P andself-inductance of the second power supply terminal N are cancelled outat least partially by mutual inductance between them. Thereby, it ispossible to reduce inductance of the power module 1.

It is preferable that the upright portion 31B of the first power supplyterminal P and the upright portion 32B of the second power supplyterminal N are 5 mm or more in height H (refer to FIG. 8), 14 mm or morein width (length in the X direction) W (refer to FIG. 7) and 2 mm orless in clearance d between them (refer to FIG. 8). In this preferredembodiment, H is equal to 5.5 mm, W is equal to 16.75 mm and d is equalto 1 mm.

In this preferred embodiment, a source electrode of each of theswitching elements Tr1, Tr2, Tr3, Tr4 and an anode electrode of each ofthe diode elements Di1, Di2, Di3, Di4 are electrically connected to theconductor layers 46, 47, 86, 87 not by using a wire but by using theconnection metal members 55, 65, 95, 105, each of which is made of aplate-shaped body. Thereby, it is possible to reduce thermal resistanceof the power module 1.

FIG. 12 is a graph which shows a ratio of thermal resistance of thepower module on the use of the flat plate-shaped connection metalmembers 55, 65, 95, 105 with respect to thermal resistance of the powermodule on the use of a wire in place of the flat plate-shaped connectionmetal members 55, 65, 95, 105 in terms of a thermal resistance ratio. InFIG. 12, the horizontal axis corresponds to the thickness (length in theZ direction) of each of the connection metal members 55, 65, 95, 105,and the vertical axis corresponds to the thermal resistance ratio.

It is apparent from FIG. 12 that the greater the thickness of each ofthe connection metal members 55, 65, 95, 105, the smaller the thermalresistance of the power module 1. This is because the connection metalmembers 55, 65, 95, 105 are increased in heat radiating effects on heatgenerated at the switching elements Tr1 to Tr4 and the diode elementsDi1 to Di4 with an increase in thickness of each of the connection metalmembers 55, 65, 95, 105. However, it is apparent that even if thethickness of each of the connection metal members 55, 65, 95, 105 isgreater than 2 mm, thermal resistance of the power module 1 is notdecreased so much. Therefore, it is preferable that the thickness ofeach of the connection metal members 55, 65, 95, 105 is from 0.8 mm ormore to 2.0 mm or less. In this preferred embodiment, the thickness ofeach of the connection metal members 55, 65, 95, 105 is 1.0 mm, andthermal resistance of the power module 1 can be reduced by about 15% ascompared with a case where a wire is used in place of the connectionmetal members 55, 65, 95, 105.

In this preferred embodiment, as described previously, the rear surfaceof the heat radiating plate 2 is polished to make thinner the heatradiating plate 2. Accordingly, it is possible to reduce thermalresistance of the power module 1.

FIG. 13 is a graph which shows a ratio of thermal resistance of thepower module where the rear surface of the heat radiating plate 2 ispolished with respect to thermal resistance of the power module wherethe rear surface of the heat radiating plate 2 is not polished in termsof a thermal resistance ratio. In FIG. 13, the horizontal axiscorresponds to the thickness (length in the Z direction) of a peripheraledge portion of the heat radiating plate 2, and the vertical axiscorresponds to the thermal resistance ratio. In FIG. 13, the thicknessof the heat radiating plate 2 is 4 mm where the rear surface of the heatradiating plate 2 is not polished.

It is apparent from FIG. 13 that the more the heat radiating plate 2 ispolished to be made thinner, the smaller the thermal resistance of thepower module is. This is because when the heat radiating plate 2 isdecreased in thickness, heat generated at the switching elements Tr1 toTr4 and the diode elements Di1 to Di4 is easily transmitted to coolingmeans such as a heat sink mounted on the rear surface (surface on the −Zdirection-side) of the heat radiating plate 2. Therefore, it ispreferable that the rear surface of the heat radiating plate 2 ispolished to make thin the heat radiating plate 2. In this preferredembodiment, the peripheral edge portion of the heat radiating plate 2 is3.5 mm in thickness, and thermal resistance of the power module 1 can bereduced by about 2% as compared with a case where the rear surface ofthe heat radiating plate 2 is not polished.

In this preferred embodiment, a thickness of each of the solder layers53, 61, 91, 101 for bonding respectively the switching elements Tr1,Tr2, Tr3, Tr4 to the element bonding conductor layers 43, 46, 83, 86 ismade thinner than a thickness of general solder. Accordingly, it ispossible to reduce thermal resistance of the power module 1.

FIG. 14 is a graph which shows a ratio of thermal resistance of thepower module where a thickness of each of the solder layers 53, 61, 91,101 is made thinner than a reference value with respect to thermalresistance of the power module where the thickness of each of the solderlayers 53, 61, 91, 101 is equal to the reference value in terms of athermal resistance ratio. In FIG. 14, the horizontal axis corresponds tothe thickness of each of the solder layers 53, 61, 91, 101, and thevertical axis corresponds to the thermal resistance ratio. In FIG. 14,the reference value of the thickness of each of the solder layers 53,61, 91, 101 is to be 0.12 mm.

It is apparent from FIG. 14 that the thinner the thickness of each ofthe solder layers 53, 61, 91, 101 is made, the smaller the thermalresistance of the power module 1 becomes. This is because when thethickness of each of the solder layers 53, 61, 91, 101 is made thin,heat generated at the switching elements Tr1 to Tr4 is easilytransmitted to the heat radiating plate 2. Therefore, it is preferablethat the thickness of each of the solder layers 53, 61, 91, 101 is from0.08 mm or more to 0.10 mm or less. In this preferred embodiment, thethickness of each of the solder layers 53, 61, 91, 101 is 0.08 mm, andthermal resistance of the power module 1 can be reduced by about 2% ascompared with a case where the thickness of each of the solder layers53, 61, 91, 101 is 0.12 mm.

A description has been so far given of the preferred embodiment of thepresent invention. The present invention can be carried out by anotherpreferred embodiment. For example, in the foregoing preferredembodiment, a MOS field-effect transistor constituted with a SiCsemiconductor device has been described as an example of a switchingelement. Other modes of switching elements such as an IGBT (insulatedgate bipolar transistor) may be applied. Further, in the foregoingpreferred embodiment, a description has been given of a constitutionequipped with a switching element and a diode element. However, thepresent invention is even applicable to a semiconductor device which isnot equipped with a diode element. Moreover, the semiconductor device isnot necessarily required to constitute a power module.

Although the preferred embodiments of the present invention have beendescribed in detail, they are merely specific examples used to clarifythe technical contents of the present invention. Therefore, the presentinvention shall not be construed as being restricted to these specificexamples and shall be limited only by the scope of attached claims ofthe present invention.

This application corresponds to Japanese Patent Application No.2015-37225 filed on Feb. 26, 2015 in the Japan Patent Office, and entiredisclosures of the application are herein incorporated by reference.

REFERENCE SIGNS LIST

-   1 Semiconductor module-   2 Heat radiating plate-   21-24 Terminal block-   31A Internal wiring connection portion-   31Aa Base portion-   31Ab Comb-shaped terminal-   31B Upright portion-   31C Inclined portion-   31D External wiring connection portion-   32A Internal wiring connection portion-   32Aa Base portion-   32Ab Comb-shaped terminal-   32B Upright portion-   32C Inclined portion-   32D External wiring connection portion-   40 First assembly-   41 First insulation substrate-   42 First bonding conductor layer-   43 First element bonding conductor layer-   46 Second element bonding conductor layer-   47 N terminal conductor layer-   55 First connection metal member-   65 Second connection metal member-   80 Second assembly-   81 Second insulation substrate-   82 Second bonding conductor layer-   83 Third element bonding conductor layer-   84 Third gate terminal conductor layer-   85 Third source sense terminal conductor layer-   86 Fourth element bonding conductor layer-   87 Source conductor layer-   95 Third connection metal member-   105 Fourth connection metal member-   P First power supply terminal-   N Second power supply terminal-   OUT1 First output terminal-   OUT2 Second output terminal-   Tr1 to Tr4 Switching element-   Di1 to Di4 Diode element

The invention claimed is:
 1. A semiconductor device, comprising: a firstpower supply terminal and a second power supply terminal which arearranged so as to be adjacent in a predetermined one direction in a planview; and a circuit element which is electrically connected between thefirst power supply terminal and the second power supply terminal;wherein, the first power supply terminal includes a first internalwiring connection portion and a first external wiring connection portionwhich are flat plate-shaped and arranged so as to face each other, withan interval kept, in a vertical direction along a plan view directionand a first coupling portion which couples an edge portion of the firstinternal wiring connection portion and that of the first external wiringconnection portion on the side of the second power supply terminal, thesecond power supply terminal includes a second internal wiringconnection portion and a second external wiring connection portion and asecond coupling portion which couples the second internal wiringconnection portion and the second external wiring connection portion andis disposed adjacent to the first coupling portion, and the firstcoupling portion and the second coupling portion are opposed to eachother, and at least a part of the first connecting part and at least apart of the second connecting part extend in the vertical direction. 2.The semiconductor device according to claim 1, wherein, the firstcoupling portion and the second coupling portion each includeplate-shaped facing portions facing each other, with a predeterminedinterval kept therebetween.
 3. The semiconductor device according toclaim 1, wherein, the first internal wiring connection portion and thefirst external wiring connection portion which are arranged so as toface each other, with an interval kept, and the second internal wiringconnection portion and the second external wiring connection portionwhich are arranged so as to face each other, with an interval kept. 4.The semiconductor device according to claim 1, wherein, the firstinternal wiring connection portion, the second internal wiringconnection portion and the circuit element are sealed inside a case. 5.The semiconductor device according to claim 1, wherein, the circuitelement includes a first switching element and a second switchingelement which are cascaded to take out output from a connection portionbetween the first switching element and the second switching element. 6.The semiconductor device according to claim 5, wherein, the firstswitching element and the second switching element each include a diodeelement which is connected in parallel in a reverse direction.
 7. Thesemiconductor device according to claim 5, wherein the first switchingelement and the second switching element are each made of SiC MOSFET orIGBT.
 8. The semiconductor device according to claim 5, wherein, thefirst switching element has a plurality of switching elements connectedin parallel, and the second switching element has a plurality ofswitching elements connected in parallel.
 9. The semiconductor deviceaccording to claim 5, wherein, a distance between the first couplingportion and the second coupling portion is shorter than a distancebetween an output terminal to which the output is connected and thefirst power supply terminal or the second power supply terminal.
 10. Thesemiconductor device according to claim 1, wherein, a clearance betweenthe first coupling portion and the second coupling portion is 2 mm orless.
 11. The semiconductor device according to claim 1, comprising: acircuit substrate on which the circuit element is mounted; wherein, thecircuit substrate is formed in a substantially rectangular shape in aplan view, and the first power supply terminal and the second powersupply terminal are mounted at an end of a circuit substrate in thelongitudinal direction.
 12. The semiconductor device according to claim11, wherein, the first internal wiring connecting portion and the secondinternal wiring connecting portion are connected to the circuitsubstrate by solder.